Feeding mechanism for sewing machines



Oct. 25, 1932. J R, MOFFATT FEEDING MECHANISM FOR SEWING MACHINES Filed May 17, 1928 2 Sheets-Sheet 1 m w n attain/M1 S Oct. 25, 1932. J. R. MOFFATT FEEDING MECHANISM FOR SEWING MACHINES Filed May 17, 1928 2 Sheets-Sheet 2 61 51 01 an S Patented Oct. 25, 1 1932 UNITED" STATES PATENT oFFicE JAMES R. MOFFATT, OF CHICAGO, ILLINOIS, ASSIGNOR TO UNION SPECIAL MACHINE COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS FEEDING MECHANISM FOR SEWING MACHINES 1 Application filed May 17,

The invention relates to new and useful improvements in feeding mechanisms for sewing machines and more particularly to a feeding mechanism including a feed dog which is moved back and forth for feeding the fabric.

A feeding mechanism of the above type is usually referred to as a four-motion feeding mechanism. The feed dog is raised into engagement with the fabric and then moved forward to feed the fabric after which it is lowered from engagement with the fabric and then returned for the beginning of another feed cycle. In this feed cycle there is a power effort necessary to raise the feed dog and a power effort necessary to move the feed dog to feed the fabric, which power efiorts are greatly in excess of the little effort re-' quired to lower the feed dog and to return it for the beginning of its cycle of movement. An object of the invention is to provide a weighted member which is eccentrically placed on the actuating shaft for the feeding mechanism so that said weighted member will counterbalance the increased power effort imposed on the shaft during the raising of the feed dog and the moving of the feed dog to feed the fabric.

In the drawings which show by way of illustration one embodiment of the invention:

Figure 1 is a plan view of the feeding mechanism and parts beneath the work support. r

Fig. 2 is an end view of the parts shown in Fig. 1 with the feed bar and feed dogbroken away and with the weighted member positioned directly beneath the actuating shaft.

Fig. 3 is a view similar to Fig. 2 but showing the weighted member positioned directly above the actuating shaft.

Fig.4 is a detail in section showing the feed bar, feed dog, presser foot, needles, and eccentric for raising the feed dog with the feed dog raised and feeding the fabric.

Fig. 5 is a View similar to Fig. 4 butshowing the feed dog lowered and in its retraction position. 3

The invention is directed particularly to a feeding mechanism for sewing machines, and

1928. Serial No. 278,489.

more particularly to a feeding mechanism of the four-motion type, that is, where the feed dog is raised into engagement with the fabric, then moved for feeding the fabric, after which it is lowered from engagement with the fabric and retracted, thus completing its feed cycle.

In a feeding, mechanismof this type when the feed dog is raised it not only lifts the fabric from the work support but necessarily lifts the presser foot with the fabric and the presser foot is urged against the work support by a strong spring so that when the feed dog is raised throughout a portion of its stroke, at least, it is lifting the presser bar against the tension of the spring and this imposes an increased power effort on the devices which lift the feed clog. When the feed dog is moved for feeding the fabric it will cause the fabric to slide along the under face of the presser foot. This imposes a slight power effort on the feed dog and the weight of the fabric which is being shifted imposes a further power effort on the feed dog. This all occurs during thefeeding of the fabric. When the feed dog is lowered from engagement with the fabric the spring urging the presser foot downward in a measure aids in the downward movement of the feed dog as long as the feed dog is in engagement with the material. During the remainder of the downward movement of the feed dog the weight of the parts aids inits' downward movement and the feed effort on the actuating shaft through the downward movement of the feed dog is, therefore, very much less than the feed effort which raises the feed dog and lifts the fabric preparatory to the feeding of the same. The retracting movement of the feed dog imposes only the power efiort on the actuating devices necessary to turn them over. There is no retarding or restraining resistance imposed on the feed dog.

The invention is directed particularly to a feeding mechanism of the above type and to a counterbalancing means which will counterbalance these intermittently increased power efforts imposed on the feed shaft. This has been accomplished by placing on the actuating shaft a weighted member which is eccentrically set thereon and this weighted member is positioned so that it is moving from a high point to a low point when the feed dog is being raised, and it is moving from a low point to a high point when the feed dog is being lowered. The feed'dog is moved back and forth by a crank at the end of the main shaft which oscillates the feed rocker. This crank is eccentrically set on the shaft and the Weighted member is placed on the actuating shaft on the opposite side of the center of the shaft, or substantially Referring more in detail to the drawings: The invention is shown as applied to a sewing machine having a bed plate 1 provided with the usual bearings 2, 2 on which the cloth plate is mounted. Located beneath the bed plate is the feeding mechanism for feeding the material across the work support as it is being stitched. The plane of the work support is indicated in Figs. 4 and 5 by the line a, a. The position ofthe stitching mechanism is indicated by the needles 3. Three needles are shown, although it is understood that any type of stitching mechanism may be used. The fabric is held on the work support by a presser foot 4 and the usual spring bears on this foot urging it toward the cloth plate to hold the material against the cloth plate during stitching and against the feed dog during feeding.

The material is fed by a feed dog 5 carried by a feed bar 6 pivoted at 7 to a feed rocker 8. This feed rocker 8 is pivoted at 9 to the bed 1 of the machine. The feed dog is raised and lowered by-an eccentric 10 mounted on an actuatin shaft 11. This eccentric 10 bears against a hardened plate on the under face of the feed bar and the hardened plate and feed bar are held in contact with the eccentricby the forked member 12.

The feed rocker is oscillated by means of an arm 13 which is rigidly secured to the rocker. This arm is pivoted at 14 to a link 15 which link cooperates with the crank pin 16 mounted on a disk 17 attached to the end of the main actuating shaft 11. This crank pin 16 is mounted in a slot 18 extending diametrically across the disk. This crank pin is adjustable in the slot so that the throw of the crank pin can be Varied. It is, of course, set eccentrically of the center of the actuating shaft and it is by virtue of this eccentric setting of the crank pin that the link 15 is moved endwise and the arm 13 oscillated, thus imparting oscillations to the feed rocker and the back and forth movements to the feed dog. The parts so far described are of the usual construction in a four-motion feeding mechanism. It will be apparent that the eccentric 10 in its raising and lowering of the feed dog imposes a variable power effort on the actuating shaft. When the eccentric is moved from the position shown in Fig. 5 to the position shown in Fig. 4 the feed dog is raised and is brought into contact with the under face of the fabric lifting the fabric from the cloth plate for the feeding stroke.

The presser foot is urged against the fabric by a spring, a well-known construction. The feed dog in raising the fabric must lift the presser foot against the tension of this spring. \Vhen the feed dog is lowered, then the presser foot will urge the feed dog downward until it passes beneath the surface of the throatplate for its return stroke. During a portion of the rotation of the main actuating shaft there is this increased power effort imposed thereon necessary to the lifting of the feed dog and cooperating presser foot and this power efiort is much less during the;

remainder of the revolution of the main shaft which brings about a lowering of the feed dog.

Mounted on the main shaft is a weighted member 19. Said weighted member 19 is shown in the present embodiment of the invention as attached to the disk 17 by suitable screws 20, 20. This weighted member completely encircles the disk and the adjusting screw 21 for shifting the crank pin, passes through a portion of the member and the member serves as a means for preventing the screw from endwise movement. The weighted member includes a part which is of the same thickness as the disk as shown in Fig. 1 and also a part 19a which is of a greater thickness and which overhangs the front face of the disk. The inner and outer edges of this part 19a are circular and the centers of the circles are out of line so that said part is tapered from the end 195 to the end 190 so as to decrease in thickness. This is for the purpose of distributing the weight so as to bring about a proper counterbalance ing of the varying power efforts imposed on the actuating shaft as the feed dog is operated. This also places all the weight possible into this overhanging flange, and at the same time, provides proper clearance for the link 15. The inner face of the flange is shaped so as to give only the necessary clearance for the link.

It will be noted that the center of the weighted member is at all times eccentric to the center of the actuating shaft. lVhen the actuating shaft is in the position shown in Fig. 2 the feed dog is just about to begin its descending movements and the Weighted member is turning in the direction of the arrow. hen the parts are in the position shown in 3 then the feed dog is beginning its rising movements. It will be apparent from the above that when the feed dog comes into contact with the material and begins to raise the presser foot the center of the weighted member is passing from a high point to a. low point in its rotation about the center of the actuating shaft, and when the feed dog is descending then the center of the weighted member is passing from a low point to a high point in its rotation about the center of the actuating shaft. Thus it is that the weighted member counterbalances the varying power effort imposed on the actuating shaft as the feed dog is raised and lowered. It helps to raise the feed dog by adding to the power effort and it, in a measure, retards the movement of the actuating shaft when the feed dog is being lowered, and thus the power effort is more nearly uniformly distributed throughout the entire cycle of rotation of the actuating shaft so far as the raising and lowering of the feed dog is concerned.

The center of weight in the weighted member is located substantially at a point directly opposite the center of the main shaft from the center of the crank pin which moves the feed dog back and forth through the oscillations of the feed rocker. When the crank pin is moving from a low point to a high point the feed dog is moving 011 its feed stroke. The center of weight is at this time moving from a high point to a low point in its rotation about the center of the actuating shaft. Thus it is that the weighted member counterbalances the off-center position of the crank pin and the increased feed effort to the movement of the fabric. When the crank pin is moving from a high point to a low point then the center of weight is moving from a low point to a high point in its rotation about the center of the shaft. Thus it is that the rotation of the weight about the center of the shaft more uniformly distributes the power effort necessary to the turning of the crank pin and the moving of the feed dog back and forth.

From the above it will be apparent that I have provided a weighted member mounted on the actuating shaft which imparts feeding movements to a four-motion feed dog, which weighted member so counterbalances the power effort necessary to the movement of the feed dog as to uniformly distribute said power effort throughout the entire cycle of rotation of the shaft. The invention is di rected to a machine which travels at a very high speed and the parts turn over several thousand times per minute. In a machine traveling at this high speed, if the power effort on the actuating shaft is unequally distributed, vibrations are set up in the frame and the frame parts which are very objectionable.

By my improvement wherein the power effort is uniformly distributed throughout the cycle of rotation of the shaft all these objectionable vibrations are avoided.

It is obvious that minor changes in the details of construction and arrangement of parts may be made without departing from the spirit of the invention as set forth in the appended claims.

Having fully described my invention, what the feed dog and a weighted member mount- '5 ed eccentrically on said shaftand with the center of the weight thereof disposed relative to the axis ofsaid shaft-so as to counterbalance the'power effort imposed on'said shaft by the raising of the feed dog and by the i moving of the feed dog to feed the fabric.

2. A feeding mechanism for sewing machines including in combination a feed dog,

a feed bar'carrying said feed dog,a main actuating shaft, an eccentric on said main shaft i connected to said feed barffor raising and lowering the feed dog, a crank pin carried by sald main actuating shaft and connected to said feed bar for moving said feed dog back and forth and a weighted member mounted eccentrically on said shaft and with the cen ter of the weight thereof disposed relative to the axis of said shaft so as to counterbalance the power-effort imposed on said shaft by the raising of the feed dog and by the moving of the feed dog to feed the fabric.

3. A feeding mechanism for sewing machines including in combination a feed dog, a feed bar carrying the feed dog, a main actuating shaft, means operated by said shaft for raising and lowering the feed bar, a disk on the end of the main actuating shaft, a crank pin eccentrically mounted on said disk and connected to the feed bar for moving the feed dog back and forth, a weighted member attached to said disk and having the center of weight disposed relative to the crank pin so as to counterbalance the power effort imposed on said shaft by the raising of the feed dog and by the moving of the feed dog to feed the fabric.

4. A feeding mechanism for sewing machines including in combination a feed dog, a feed bar carrying the feed dog, a main actuating shaft, means operated by said shaft for raising and lowering the feed bar, a disk on the end of said main actuating shaft, a crank pin eccentrically mounted on said disk and connected to the feed bar for moving the feed dog back and forth, a weighted member mounted on said disk and having the center of weight disposed relative to the crank pin so as to uniformly distribute the power effort imposed on said shaft by the actuation of the feed dog throughout the entire cycle of rotation of the shaft.

5. A feeding mechanism for sewing machines including in combination a feed dog, a feed bar carrying the feed dog, a main actuating shaft, means operated by said shaft for raising and lowering the feed bar, a disk mounted on the end of said shaft, a crank pin carried by said disk and connected to the feed bar for moving the feed dog back and forth, a Weighted member surrounding said disk and attached thereto, said weighted member having an eccentric portion overhanging the disk and disposed so as to uniformly distribute the power effort imposed by the actuation of the feed dog on the actuating shaft throughout the entire cycle of rotation of the shaft. 7

:6. A feeding mechanism for sewing machines including in combination a feed dog, a feed bar carrying the feed dog, a main actuating shaft, means operated by said shaft for raising and lowering the feed bar, a disk mounted on the end of said shaft, a crank pin carried by said disk and connected to the feed bar for moving the feed dog back and forth, a weighted member surrounding said disk and attached thereto, said weighted member having an eccentric portion overhanging the disk and disposed so as to uniformly distribute the power efiort imposed by the actuation of the feed dog on the actuating shaft throughout the entire cycle of rotation of the shaft, said overhanging eccentrio portion of the weighted member being tapered from its advance end toward the rear end thereof.

In testimony whereof, I afiiX my signature.

JAMES R. MOFFATT. 

